You should try scrubbing with bleach, because mantras and sadhanas won't remove so called "negative karma". They aren't miracle products. Recitation of mantras & sadhanas only provides the opportunity to purify negative karma. But it is your own mind that creates the problem to begin with. So, you have to work with that.

If you plant the seeds of negative results through the actions of your body, speech and mind, then that is what you will end up harvesting.

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Profile Picture: "The Foaming Monk"The Chinese characters are Fo (buddha) and Ming (bright). The image is of a student of Buddhism, who, imagining himself to be a monk, and not understanding the true meaning of the words takes the sound of the words literally. Likewise, People on web forums sometime seem to be foaming at the mouth. Original painting by P.Volker /used by permission.

"All memories and thoughts are the union of emptiness and knowing, the Mind.Without attachment, self-liberating, like a snake in a knot.Through the qualities of meditating in that way,Mental obscurations are purified and the dharmakaya is attained."

Since i am not a monk, neither an expert in Buddhism, my answer will only express what i think that may be the view used by Buddhism.

You can do something good about your negative Karma (see below), but you must know that our Karma cannot simply disapear. You cannot make your Karma go away. As soon you make any action (physical action, verbal action or even toughts) you are already generating Karma. The seeds of that Karma may grow up and take effect right away, a few seconds later, or even days, years or in your next life(s). A very simple and linear example: you call a ugly name to a big and bad guy on the street (you are generating bad Karma), then, as a consquence, the big bad guy will punch in your face and that will hurt a lot (ok, stupid example lol). You suffered the consequence of your bad Karma. Or...you call the name to a guy in the street but he ignores you...who knows, you may suffer the consequences of such bad karma within 5 life times, or within billion years. Maybe you will never suffer because of that: not every action will have time take effect because in the meanwhile you may reach Nirvana for example. Not every action will create a result with meaning, a Karma with significant impact. Maybe calling a bad name to a guy on the street will just make him moan and groan for a little and thats it.

With that in mind, what can you do about bad Karma? Well, since i am a Pure Land Buddhist my answer will be just accordingly to that. You must investigate carefully what other Buddhist Schools have to say. But before that i will tell you first what in general Buddhism says: avoid bad actions! Generate Bodichita as someone said here. Cease all bad toughts. Clean your mind with meditation and have peace with that. Do the precepts and avoid any bad action (verbal or physical) and do good actions. Have a good mind towards every people and every being and wish them (even if they are bad to you) the best. With such actions you will generate good Karma that may counteract a little the bad Karma you may have. Maybe such seeds of good karma may delay the bad ones. But remember that even Buddha (while in the physical form of Shakyamuni Budhha or Siddharta Gautama) could not avoid bad Karma! Thats something to bear in mind: no one will escape to bad (or good) Karma completly until Nirvana.

Now, what you can do according to Pure Land Buddhism is to do Nembutsu: recite the name of Amitabha Buddha with a single mind.

Doing recitation will rippen away thousands of seeds of bad Karma. It is said that recitation can stop (so to say) the Karma of previous lifes aeons ago.

There you can read:"All evil karma results, ultimately, from delusion, the antithesis ofenlightenment. Such practice as Buddha Recitation leads ultimatelyto enlightenment and thus dissolves away evil karma. It is as thougha house were boarded up for ten thousand years. As soon as a windowis opened, eons of darkness disappear in a split second. [...]By sincerely invoking Amitabha Buddha’s name, which isin reality identical with Amitabha himself, we identify ourselves withAmitabha. As a result of this identification, a portion of his meritsis transferred to us. These merits, which are now ours, are sufficientnot only to counterbalance the effects of our evil actions but alsoto ensure our rebirth in the Pure Land. The law of karma has notbeen suspended for our benefit. All that has happened is that a morepowerful karma has cancelled out one that was weaker."Hope that this was useful for you

The best way to remove negative karma is actually stay at your primordial state.

In that state, actually has no positive and negative karma anyway.

I am not here nor there.I am not right nor wrong.I do not exist neither non-exist.I am not I nor non-I.I am not in samsara nor nirvana.To All Buddhas, I bow down for the teaching of emptiness. Thank You!